Bally Gas Display replacement (prototype just for fun)

[Homepin]

Some of you may know that when I was last in Brisbane I bought an old Bally that had been converted by an Italian company into a game called "Movie Masters". I wanted it for a test bench for the upcoming MPU project. When I collected it from Robs place in Townsville it looked a little sad but it was complete which is what I wanted.

It didn't take much to get the MPU going (bad 5101 RAM mainly) but most of the gas displays had seen better days - missing segments, burnt glass etc. so I thought I would have a look at whipping up my own replacement from common parts and with what I had on hand. I chose a 4511 BCD decoder as it is very close in specs to the original (hard to get) chip. I didn't realise at the time I was laying out the PCB that a couple of the input pins require signals that are inverted from the original and you can see the couple of transistors I 'bodged' onto the board when I realised this later during testing.

Yes, the displays I had to hand are smaller than the originals and are blue BUT, I am encouraged by this result and I might search for some larger orange 7 segment LEDs and make up a full set for this machine. All the parts used are very common and inexpensive - most available over the counter from Jaycar etc.

One major advantage is that the entire display runs on the 5 volt rail so the 180V would not be required. I am unsure how much interest there might be for a full set of DIY - assemble yourself displays in orange and as close to the originals as possible??? Maybe not enough to warrant developing things further, hard to know? In any case I guess I won't have to try and track down the replacement glass for this test machine 

The sample boards:



Assembled (and the bodge):



Fits nicely - and WORKS!:



and looks great in 'display test mode' (you can see the last digit is out on the original display in this video):

[Retropin]

Thered be more demand than you think Mike. The time i spend fixing the old ones could be better spent building new ones.
Put it this way... i have BALLY games that are missing displays.. i took ALL perfect displays out of my Star Trek so i could sell a SPECTRUM. ST is a keeper and so i try and find old displays that i can fix up to put in there. Only way i have of really doing this is to buy bulk lots off Ebay... chuck out those with burnt anodes etc and repair the rest... its a hit and miss method.
Unfortunately, the old displays cannot be repaired, i have the equipment to regas these but the way they are manufactured means that this cannot be done.
The HV section on a pinball doesnt bother me at all.. it gets a bad rap, but it is only 180v.. hardly high voltage and its current is minimal... im guessing 20mA maximum if that.

Im not adverse to replacing displays with LED type.. i dont actually mind the look of these and after all, when these games were being made LED watches were hot and new on the market... remember the "Black Watch"?... my uncle had one... WOW!!! Had time and at the press of an obscure button told you the date!

Theres nothing new about having LED number displays... it was cutting edge in late 70's.. in all honesty, the pinball manufacturers really should have embraced them then.... look at my RALLY game that you saw.. cutting edge Nixie displays in the late 60's.... really advanced stuff for its time.

Personally, id be making these LED displays to replace my old ones as they died.. and die they will.

Another smaller market for you would be for Zaccaria games.. ( here we go again!) but these displays are nigh on impossible to replace... try sourcing some 7 digit!

[Homepin]

OK - interesting feedback. I will look into the price of 7 segment LEDs that are as close as I can find to the originals. I do remember last China trip I tried to find them with a 'comma' but they simply are not made. Pinled have theirs specially made. I hate to think of the min order qtys for that...............

The rest of the parts are all very VERY common and dirt cheap so the main cost would be the displays and the PCB's.

I would also like to take some accurate measurements to determine exactly how much current they would draw from the 5 volt rail and perhaps build something into the replacement boards that generated the 5 volts to run them to ease the load on the original power supply??

Any other interest in this as a project?

PS - I will add that the chip I have used - the BCD decoder - does NOT provide a 'tail' on the 6 or the 9 (you can compare in the youtube video with the original display) - I don't know how important this would be for people???

[bossgp]

simply fantastic, great idea

[ddstoys]

As Gav said im sure there would be a demand for these displays each bunch i buy off fleebay im lucky if i salvage one useable display and would much rather be piecing together one of your kits

[Strangeways]

I used to buy bulk lots off eBay years ago. $20 would buy you at least a dozen. I'd buy them to repair them and leave them aside. They SELL for over $20 each these days. so there IS demand for them. Especially 6 Digit. It costs anywhere between US$33 - $40 for a 6 digit glass. Not cheap !

So I'd think there would be heaps of interest.

[Steevsee]

Nice work once again Mike. 
Don't you ever sleep?

[Pop Bumper Pete]

EDITED

[FirePower]

Looks like a useful thing to keep more pins alive, got to be good.

Leon of test rom fame has published a few suggestions, but these are far less elegant and perhaps beyond the scope of most of us.
Mike's offering is much neater and more elegant. 

http://home.scarlet.be/~cv006274/ledbal/eled.htm  for Bally
http://home.scarlet.be/~cv006274/dispwill36/edispwill36.htm  for WMS

Leon suggests supplementing the 5V supply.

[Homepin]

"Leon suggests supplementing the 5V supply."

Yes he does and I agree with the idea but not some of the suggested 'fixes'.

I am working on a stand alone 5V PCB that would be used to run these displays only and would generate its own 5V supply so it wouldn't cause any strain on the existing (already stretched) power supply in the machine.

It seems there is enough interest so I will persue afull size digit version. I have to have 100pcs of PCBs made minimum order but realistically that is only 20 'sets' of displays..…..

I have been asked about other colours so maybe I could supply them with option to choose Orange, Green, Blue or White displays???

[Retropin]

RGB displays???

[Strangeways]

Orange would be the predominant color I'd suggest.

[Homepin]

Orange would be the predominant color I'd suggest.

I agree and Orange is also the hardest colour to find in 20mm 7 segment displays 

[Retropin]

Thats because orange colour is harder to make than standard Red, Blue, Green... even white.
White is produced by using blue with a phosphour coating.
Red, Green,Blue as we know are primary light colours.. these come easy

Orange is made by manipulating a "yellow" coating. Its colour is not as stable as any of its red partners etc.
The most unstable colour is pink.


This whole concept is funny.... i make neon signage and for years we have strived to make rich deep reds... this comes by using expensive coloured Italian made glass... it is an absolutely beautiful colour though... VERY rich and deep.
The "orange"colour of these displays is just the natural colour of neon gas... it fades out to an orange when inside wide diameter tubing.. such as the displays... the smaller the cubic area to be covered, the more RED the gas appears, but it comes at a cost of higher resistance within the gas due to a higher pressure required at filling... this in turn requires a higher voltage to strike the arc consistently.

For 25 years i have heard... "its a bit orangey... any chance it could be redder?"


Now we have the opposite scenario.

The grass is always greener....er... redder... er orangeyer    LOL!!!

[63wizz]

im sure there would be much interest in the do it your self displays just as there is in the do it your self MPU.
more projects to add to the list Thanks Mike, im far from an electronic expert but these kits are going to be fun to build

ian